In a semiconductor fabrication process, at least one, generally plural pieces of material such as semiconductor wafers (hereinafter simply called “semiconductor wafers” for the sake of brevity) under processing are placed in a container called “FOUP” (Front Opening Unified Pod) or “FOSB” (Front Opening Shipping Box), and are transferred in a substantially-sealed state to a semiconductor fabrication facility by a transfer apparatus.
Until the semiconductor wafers are transferred to a processing chamber in the semiconductor fabrication facility, they are maintained out of contact with the external air. Upon processing, they are taken out of the container by an atmospheric transfer unit such as an atmospheric transfer robot, and are moved into the processing chamber via a transfer chamber.
The atmospheric transfer unit in the semiconductor fabrication facility is, therefore, equipped with a handling apparatus called “load port”. While maintaining them in the substantially sealed state, this load port makes it possible to take the semiconductor wafers out of the container, for example, an FOUP and to transfer them into the processing chamber of the semiconductor fabrication facility, so that in the processing chamber, processing is applied to the semiconductor wafers as needed.
As appreciated from the foregoing, a load port is an apparatus equipped with a function and structure required to bring the interior of a semiconductor fabrication facility into communication with a container and then to take semiconductor wafers out of the container or to place semiconductor wafers in the container while sealing the container from the exterior, and is known conventionally (see, for example, JP-A-2004-165458).
The above-described conventional load ports are, however, configured without taking into consideration a pressure difference between an internal atmosphere of a container and that of a semiconductor fabrication facility. As soon as a door of a load port is opened to bring the interiors of the container and semiconductor fabrication facility into communication with each other, the internal atmosphere of the semiconductor fabrication facility flows into the container due to the pressure difference, thereby developing a problem that particles are carried into the container from a drive unit for the door, an atmospheric transfer robot and the like and deposit on semiconductor wafers to contaminate them.
With a view to eliminating the above-described problem, some other conventional load ports are known to include a fan arranged in an upper or lower part of a transfer chamber as a space through which semiconductor wafers are transferred inside a semiconductor fabrication facility. Even with such a conventional load port, however, it is difficult to produce an air stream to such an extent as reaching inside a container such as an FOUP arranged on the load port. When processing is performed with corrosive gas within the semiconductor fabrication facility, there is a potential problem that the load port may be caused to corrode around the container.
Conventionally-known load ports also include those of the construction that a drive chamber, in which a drive actuator for opening or closing a door of each load port is accommodated, is isolated from a transfer chamber by a partition plate and the partition plate is provided with guide slots to permit movements of a member by which the door itself or a carrier connected to the carrier and the drive chamber are linked to each other. These conventional load ports, however, involve a potential problem that corrosive gas existing in the transfer chamber enters the drive chamber through the slots and may cause corrosion of the carrier around its part connected to the above-mentioned member and also corrosion of the drive actuator to produce particles. There is another problem that such particles may deposit on semiconductor wafers. With respect to these potential problems, no consideration was taken in the above-described conventional art.